The majority of immunoglobulin in tears is of the IgA class, which is produced mainly by plasma cells of the lacrimal gland. The mechanism responsible for the lodging of IgA plasma cells in this gland is unknown, and probably not dependent on direct glandular encounter with antigen. These studies undertaken in this project are designed to examine possible microenvironmental aspects within glandular tissue effecting the lodging of IgA lymphoid cells. Experiments during the current budget period demonstrated the non-antigen requirement for homing, and differentiation of pre-committed lymphoid cells, and suggested a glandular factor capable of causing the differentiation of IgA committed lymphoid cells to mature plasma cells. Similar in vivo studies will be performed using lacrimal gland in order to determine if such glandular factors could constitute part of a general mechanism for lymphocyte activation. Co-culture experiment will observe the effort of glandular tissue on differentiation and proliferation of lymphoid cells. Some studies already indicate that mammary tissue can stimulate blast transformation in a small percentage of a mixed lymphocyte population from the rabbit. Secretory component, a protein found within the lacrimal gland, will be observed for its ability to cause preferential lodging of IgA committed cells to the rabbit cornea. The pure protein will be embedded into a slow release gel, and placed into the rabbit cornea. The surrounding cornea will be observed at various time periods for the presence of IgA plasma cells. It is hoped that such studies will lead us to a better understanding of the secretory IgA immune system which is present in tears and lacrimal gland. Such information may provide a better understanding of the immunopathogenesis and the prophylaxis (vaccines) of various conjunctival and corneal diseases.